The galvanic cell/battery has become a primary source for many portable electronic devices such as radios, hearing aids, watches, calculators and the like. In order to maintain the overall electronic devices as compact as possible, the electronic devices are usually designed with cavities to accommodate batteries as their power source. The cavities are usually made so that a battery can be snugly positioned therein, thus making electronic contact with appropriate terminals within the device. To accommodate the electronic component manufacturers, the battery industry has adopted several conventional size cells which the manufacturer can rely upon in designing their devices which require portable power sources. Due to the large number of battery-powered devices on the market, there has been a demand for increased power output capacities of standard size cells. Accordingly, various anode-cathode couples have been employed so as to provide a sufficient output capacity to operate various devices. A problem has been encountered, however, when the density of the electrode bodies has to be increased in certain cell systems if maximum output power is to be achieved. Consequently, when increasing the density of the electrode bodies many problems are encountered and they are addressed in a variety of ways. For example, organic electrolyte cells utilizing solid depolarizers have gained considerable interest for applications usually filled by aqueous alkaline cell systems. However, one drawback in the use of organic electrolyte cell systems is that they have relatively low conductivities compared to conventional aqueous cell systems of equivalent size and construction.
To increase the interfacial area contact between active cell components and thereby decrease the resistance of the cell, coiled electrode assemblies have been employed. This type of cell construction employs spirally rolled or coiled electrode assemblies (jelly roll construction) which are widely known in the battery art and are usually placed in a composite housing which serves as the current conductive terminals for the cells. In such structures, the electrode of one polarity is generally electrically connected to a conductive housing portion, and the electrode of the opposite polarity is generally electrically connected to another conductive housing portion which is insulated relative to the electrically conductive first-mentioned housing portion. The electrical contact between each electrode and its respective housing portion is generally formed by an elongated flexible electrically conductive connecting tab or element which is secured at one end to the electrode and at the other end is secured to the respective housing portion.
The current collector tabs are attached to the electrodes (or electrode carriers), usually by welding. This technique involves time-consuming manual operations in cell assembly procedures which reduces line productivity and adds to the manufacturing costs. The problems associated with such manual operations become more difficult when the above-mentioned techniques are applied to smaller size cells.
It is therefore an important object of this invention to provide an electrical contact between an inner exposed electrode of a coiled electrode assembly and an electrically conductive terminal using a flexible electrically conductive member.
It is a further object of this invention to provide a sealed galvanic cell having a coiled electrode assembly construction in which the danger of cell shorting due to tearing of the separator during cell assembly is reduced.
It is another object of this invention to provide a flexible electrically conductive member that is secured inside the galvanic cell by the clamping coaction of an inner cover and an outer cover.
It is another object of this invention to provide a coiled electrode assembly cell that is inexpensive to manufacture and easy to assemble.
The foregoing and additional objects will become fully apparent from the following description and the accompanying drawings.